The present invention relates to a magnetic head device including a slider having a magnetic head mounted thereon, a resilient suspension structure carrying the slider and a head IC chip. The present invention further pertains to a magnetic disc device provided with such magnetic head device.
In conventional magnetic head devices having a magnetic head for writing and/or reading information on a magnetic recording medium such as a magnetic disc, it has been common to mount the magnetic head on a slider which is maintained in a floating relationship with respect to the magnetic recording medium. The slider is generally formed from a resilient metallic material sheet which is arranged to extend from a movable arm structure and supported by a suspension member.
The movable arm is provided for supporting one end of the suspension member and it has been common to mount a head IC chip on the movable arm. The head IC is provided for including electronic circuits for amplifying writing current which is to be suppled to the magnetic head and reading voltage from the magnetic head, and for controlling the writing and/or reading operation. In an arrangement wherein the head IC chip is mounted on the movable arm, an increased length of connecting lead is required between the head IC chip and the magnetic head and this increased length of the connecting lead may be a cause of noise generation. Such increased length of the connecting lead may produce a parasitic capacitance and an inductance which have an effect of undesirably increasing rising time and falling time of pulse signals. Thus, high speed data transmission will be disturbed.
In order to solve the problems, there has been proposed by the Japanese Laid-Open Patent Publication No. Sho 53-69623 to mount the head IC chip on the slider. Further, the Japanese Laid-Open Patent Publication No. Hei 3-108120 proposes to divide the head IC into an IC main body and an IC sub-body, and mount the IC main body on the movable arm supporting the suspension member and the IC sub-body on the slider or the suspension member.
In these known structures, it is possible to decrease to a certain extent the distance between the head IC chip and the magnetic head so that it may be possible to suppress noise which may otherwise be produced because of the length of the connecting lead. However, the structure has another unsolved problem in that the temperature of the IC chin is increased due to the writing current which flows through the head IC chip during recording operation. It should further be noted that in the structure the IC chip is located close to the magnetic head so that the magnetic head may receive an adverse thermal effect from the head IC chip which generally generates heat in operation.
More specifically, in a structure where the head IC chip is mounted on the movable arm which has a sufficient thermal capacity as well as a substantial area for heat radiation, the temperature of the IC chip can be maintained sufficiently low. Further, since the head IC chip is located far from the magnetic head, there is least possibility that the magnetic head is adversely affected by the heat generated in the head IC chip. To the contrary, where the head IC chip is located on the slider, it is difficult to ensure sufficient surface area for heat dissipation so that it cannot be expected to have the temperature of the IC chip decreased through dissipation of heat. It should further be noted that the slider usually has a limited thermal capacity so that it cannot be an effective tool for providing a temperature deacrease through thermal conduction. As the result, there will be a possibility in the aforementioned structures that the temperature of the head IC chip is undesirably increased to an extent that the reliability of the IC chip will be lowered. It should further be noted that since the magnetic head is located close to the head IC chip the magnetic head is thermally affected by the heat generated in the head IC chip. Thus, the temperature of the magnetic head itself may increase to an unacceptable level. Similar problem will also be encountered in a structure where the head IC chip is located on the suspension member if the location of the head IC chip is close to a tip end of the suspension member.
It is therefore an object of the present invention to provide a magnetic head device of the type as described above wherein the temperature increase in the head IC chip can be suppressed to a satisfactory level and the heat generated in the head IC chip is effectively prevented from being transmitted to the magnetic head.
It is another object of the present invention to provide a magnetic head device wherein noise caused by the connecting lead between the head IC chip and the magnetic head can be suppressed so that a high speed data transmission is made practical.
It is another object of the present invention to provide a magnetic disc device which includes the aforementioned magnetic head device.
According to one aspect of the present invention, there is provided a magnetic head device including a slider having a magnetic head thereon, a suspension structure having one end supporting the slider, and a head IC chip which is mounted on said suspension structure at a side adapted to face a recording medium.
According to another aspect of the present invention, there is provided a magnetic head device including a slider having a magnetic head thereon, a suspension structure formed from a resilient metallic sheet and having one end supporting the slider, and a head IC chip, the suspension structure being attached at the other end to another member such as a movable arm, the head IC chip being mounted on the suspension structure at a location defined by 0.2xe2x89xa6Lb/Laxe2x89xa61, where La is a distance between the slider and the point of connection of the slider to the aforementioned other member, and Lb is a distance between the slider and the head IC chip.
In the aforementioned aspect of the present invention wherein the head IC chip is mounted on the suspension structure at the side facing the magnetic recording medium, the magnetic recording medium is moved relative to the slider and the head IC chip and there is produced flow of air between the magnetic recording medium and the slider and also between the magnetic recording medium and the head IC chip. Usually, the slider and the head IC chip are held stationary and the magnetic recording medium is in the form of a rotatably driven disc. Then, flow of air is produced as the magnetic recording disc rotates in the vicinity of the surface of the disc and serves to cool off the head IC chip. As the result, the temperature of the head IC chip can be suppressed to a substantially low value.
In this aspect of the present invention, it is preferable that the height of the head IC chip as measured in the mounted state from the suspension structure is smaller than the height of the slider. In this instance, the head IC chip is preferably in the form of a bare chip which is preferably mounted or attached to the suspension structure by means of flip-chip-bonding. By adopting the flip-chip-bonding for mounting such bare chip, it is possible to decrease the height of the head IC chip in the mounted state. Therefore, with this arrangement, the IC chip can be mounted on the recording medium side of the suspension structure without having any risk of the head IC chip interfering with the magnetic recording medium in use.
In an arrangement wherein the suspension structure is attached at the other end to the other member such as a movable arm, it is preferable that the location of the head IC chip on the suspension structure be, in terms of La which is a distance between the slider and the point of connection of the slider to the aforementioned other member, and Lb which is a distance between the slider and the head IC chip, within a range 0.2xe2x89xa6Lb/Laxe2x89xa61, more preferably within a range 0.3xe2x89xa6Lb/Laxe2x89xa60.7, and most preferably within a range 0.4xe2x89xa6Lb/Laxe2x89xa60.6.
In a structure wherein the head IC chip is mounted on the suspension structure, it may be possible because of a thin structure of the suspension that heat may not be sufficiently dissipated nor conducted depending on the location of the head IC chip as described with reference to the prior art. Thus, there is a risk that the temperature of the IC chip is increased to an unacceptable level and the magnetic head may receive an adverse thermal effect from the high temperature IC chip. It has now been found that the temperature of the head IC chip is greatly increased when the IC chip is mounted on the suspension structure at a location close to its tip end. The reason for this is understood that the thermal conduction takes place substantially in one direction only so that the IC chip cannot be cooled off sufficiently. It has also been realized that the temperature of the magnetic head increases higher as the location of the IC chip becomes closer to the tip end of the suspension structure. This is because the IC chip which is considered as a heat source is located close to the magnetic head. It has also been found that, in the structure of the aforementioned prior art wherein the head IC chip is mounted on the slider, both the temperature of the IC chip itself and that of the magnetic head increase to an extremely high level.
It should be noted that in the aforementioned aspect of the present invention wherein the head IC chip is mounted on the suspension structure at the side facing the magnetic recording medium and the location on the suspension structure in the range as defined, it is possible to maintain the temperature of the IC chip sufficiently below an acceptable level and to suppress the temperature of the magnetic head to a low value.
The suspension structure may be made of a resilient metallic material such as a corrosion resistant steel. It is preferable that the head IC chip be attached to a surface of the suspension structure through a layer of an electrically insulating material such as a resin material like polyimide.
In a preferable mode of the present invention, the suspension structure comprises a load beam formed from resilient metallic material such as a corrosion resistant steel, and a flexure member made of a resilient metallic material such as a corrosion resistant steel having a width smaller than the load beam and provided on a side of the load beam where the head IC chip is to be attached. It is preferable that the flexure member is coated with a first layer of an insulating material such as a resin material like polyimide, and at least one conductive layer is provided on the first insulating layer to form a portion of connecting lead or leads for connection with the magnetic head and the head IC chip. It is also preferable to cover the conductive layer with a second layer of an insulating material such as a resin material like polyimide. In this instance, it is preferable to locate the head IC chip on the second insulating layer and connected with the conducive layer by soldering.
In the mode of the present invention wherein the head IC chip is mounted on the suspension structure at the side facing to the magnetic recording medium, it is preferable that the surface of the head IC chip facing to the magnetic recording medium has such a configuration that a substantial heat dissipating area can be ensured. More specifically, the head IC chip may have a wide and flat surface at the side facing the magnetic recording medium. Alternatively, the head IC chip may have a rough surface at the side facing the magnetic recording medium or an undulated surface as well. In another alternative structure, the head IC chip may be formed at the side facing the magnetic recording medium with one or more grooves for allowing flow of air to pass through. The groove or each of the grooves may have a width which is large at an end opposite to the direction of movement of the magnetic recording medium with respect to the head IC chip and gradually decreasing toward the direction of the movement of the medium.
It is preferred that the head IC chip has a mass less than 1.0 mg so that the head IC chip may not have any adverse effect on the mechanical vibration characteristics of the suspension structure when the chip is mounted on the suspension structure.
It is further preferable in the magnetic head device and the magnetic disc device having a magnetic recording disc located to be opposed to the magnetic head of the magnetic head device that the spacing between mutually facing surfaces of the head IC chip and the magnetic disc is maintained to be less than 1000 xcexcm. It has been found that with this arrangement, the cooling effect of air flow can be enhanced and the temperature of the head IC chip can always be maintained below 150xc2x0 C.
It should further be noted that in another aspect of the present invention there is provided a magnetic disc device comprising a magnetic head device and a rotatable magnetic recording disc. The magnetic head device includes a slider having a magnetic head thereon and a suspension structure having one end supporting the slider. The magnetic head is arranged so that it is faces the magnetic head of the magnetic head device. There are provided a head IC chip and at least one connecting lead member for connecting the magnetic head with the head IC chip. The head IC chip is mounted on the connecting lead member at a location where the head IC chip is always exposed to flow of air which is produced by a rotation of the magnetic recording disc.
According to the arrangement wherein the head IC chip is mounted on the connecting lead member at a location where the head IC chip is always exposed to flow of air which is produced by a rotation of the magnetic recording disc, the head IC chip is always exposed to a cooling air flow throughout the stroke of the movement of the magnetic head between the inner and outer peripheries of the recording area of the magnetic recording disc so that the temperature increase in the IC chip can be substantially suppressed.
It is preferred that in the aforementioned arrangement the head IC chip is located radially inside the outer periphery of the magnetic recording disc and is opposed to the disc. It is also preferable in order to enhance the cooling effect by the air flow that the distance between the opposing surfaces of the head IC chip and the rotating magnetic recording medium is maintained to be less than 1000 xcexcm. It is possible with this arrangement to suppress the temperature of the head well below 150xc2x0 C.